Styrene, also known, as vinyl benzene, is an aromatic compound that is produced in industrial quantities from ethyl benzene. The most common method of styrene production comprises the dehydrogenation of ethylbenzene, which produces a crude product of styrene monomer and unreacted ethylbenzene and hydrogen. Polystyrene is an aromatic polymer produced from styrene monomer. Polystyrene is a widely used polymer commonly found in many commercial applications.
Many industries seek to replace the metals used for structural materials with plastics. Plastics like polystyrene are typically lighter and less expensive than metals. Plastics may also be used as thermal or electrical insulators because they do not typically interfere with magnetic or electrical signals. Polystyrene is a durable and inexpensive polymer that is frequently encountered in daily life. However, polystyrene is typically weaker than metals. Thus, polystyrene is commonly combined with other polymers or composite materials such as fibers to provide improved strength and other properties. Some of the varied applications of polystyrene include insulation, foam cups, disposable cutlery, food packaging, office supplies, CD/DVD cases, housewares, appliance linings, cosmetics packaging, toys, computer housings, bottles, tubing, and dunnage.
Polystyrene containing products are often discarded and only a small fraction of discarded polystyrene products are recovered and recycled. In addition, byproducts and excess amounts of polystyrene and polystyrene containing compositions are produced during the process of molding, shaping and producing the products containing polystyrene. These byproducts, along with post consumer polystyrene products, often become waste. This waste typically ends up in landfills, or incinerators, or sometimes results in litter. Most of these products are non-biodegradable and thus remain long after disposal.
Poly(lactic acid) or PLA is a bio-derived, biodegradable and compostable polymer. Use of PLA as a biodegradable modifier to polystyrene brings additional marketable “environmentally friendly” value to commodity polystyrene and can add a biodegradable aspect to the otherwise non-biodegradable commodity polystyrene. However, combining these two materials has proven to be difficult. PLA and polystyrene form an immiscible polymer blend when combined, therefore, the combination of the two materials into one homogenous phase has been difficult. These heterogeneous mixtures of polystyrene and PLA have not resulted in products that can replace stronger, non-biodegradable, polystyrene blends currently on the market.
It would thus be desirable to obtain a homogenous polystyrene blend containing PLA. It would also be desirable to obtain a biodegradable polystyrene blend that is strong enough to be used in a wide variety of applications.